Smash rocks to test how planets form

CALL it the anti-Large Hadron Collider. Instead of smashing small particles together at high speeds, researchers have collided giant granite spheres at low ones.

The idea was to look into the formation of planets and asteroids, which coalesced from collisions between bits of rock in the early solar system. Previous studies showed that marble-sized stones bounce off each other like billiard balls.

In the case of boulders, however, it was assumed they would slow after impact to 50 per cent of their initial speed, as some of the collision energy would be absorbed, resulting in changes such as cracks.

Now, Daniel Durda of the Southwest Research Institute in Boulder, Colorado, and colleagues have tested this idea. They dangled two 1-metre-wide granite spheres from cranes and knocked them together 108 times at up to 1.5 metres per second.